There can be perfectly legitimate reasons to sell a guild.
At one point my guild merged into another guild. The old guild was well built up and relatively high level; once we merged, it was dormant, with only some alts left around and a few inactives that we hoped would log on and come over to new guild.
Then another guild split up, and the splinter faction wanted a new guild. They did not want to build it from scratch and sink all the money and resources into leveling castle, my old guild leader still had control of a good guild castle. So, it was a good match. They got a good new home, we got some in-game loot (well, my guild ex-leader did, the lil greedy !@#%, we did not. :p).
-- Rustyx --- 92R / 92S / 92M on Reni (Guild KnightShift). Yes, running the new FOTM R/M, cause I am not elf enough to be WD/S.
Oh, and people who have more than 3 classes are clinically insane.